Method of making composite titanium pigments



Patented Oct. 14, 1941 UNITED STATES PATENT OFFICE METHOD OF MAKING COiMBOSITE TITANIUM PIG'MENTS Lonnie W. Ryan, Westfield, N. J., a nd Winfred Joseph Cauwenberg, PineyBiver, Va assignors to Int-erchemical Corporation, NewI'York, N. 'Y'., a corporation'of Ohio Q No Drawing. Application June 1,1839,

Serial No. 277,810-

This invention relates to the manufacture of colloidal hyd'ratedTiOais unnecessary and undecomposite pigments containing titanium dioxide sirable because of the harmful eifect on the final and inert extenders such as calcium sulfate, and p me t pr p s and n the handling p p has particular reference to a new and novel methties of the'precipitate. 0d of precipitating such pigments, characterized Example. 1

by very rapid admixture of a titanium sulfate solution with a slurry of the extender, whereby A5 a typlcal example of 0111 Invention, We D pare 700 pounds of anhedral gyp Crystals,

pigment of improved properties is obtained.

In the manufacture of composite pigments confe y y rehydretine lly dehydrated taining titanium dioxide and extenders such as 10: ypsum, @j O i 9; e-me th0d described in our calcium sulfate, a great many methods have been eQe e l e 9 3 9 Serial um 138,104 adopted. In the early stages of the development le A r 2 93, HOW Patent 2,207,415, of these pigments, they were prepared by adaf?? f q- Ju y 9 mixing soluble calcium salt solutions with titani- The 700 pounds of rehydrated gypsum are then um sulfate solutions and boiling the mixtures to 15- e nl ap bble mill toge With 158 precipitate hydrolyzed basic titanium compounds ens f- Water containing 2.45 pounds of hydrated on the freshly precipitated calcium sulfate, foll --C a(O I-I 2 and 1. P01111615 f um S111- lowed by filtration, Washing and calcination. Befite and milled for about "W hours whereby the cause of the difilculty of controlling the calcium g l m ra yp m Pa e e dispersedsulfate crystal formatio by t t t- 20, This milling breaks down the agglomerate structempts were made to admix separately prepared W fe slur'ries of calcium sulfate with precipitated 121- V TheimiHed-gYDSllI-YbWeter Slurry s a s erred tanium dioxide slurries, filtering, Washing and cal- 9 a tank d 117 gallons of Water at 100 C. and cining the mixture. This gave relatively poor ad- QO'IIlT'aihiIig about 'P -fi f Sulfuric acid mixture of the constituents. The industry has addede p 'fe is bldught t about generally adopted still another method which andv 1930' P 1 5 Of an ilmenite Ore solugives perfect admixture, improved pigment prop. tlOll, all) 3', tmpela-UJIE Of 65 Cl, and from which a erties and low operating costs. This method in- D3151? ofth n, has been removed by Crystallizavolves preparing calcium ulfate slurry of pretion as ferrous sulfate, and containing about 5 determined crystalline characteristics, admixing grams D liter of nous sulfate calculated as it with a titanium sulfate solution, and heating T102, and analyzing as follows, are added during the mixture to cause hydrolytic precipitation of about /2 mmutel the titanium in the presence of the calcium sul- Per cent fate. 11.6

We have discovered that greatly improved pigsulfllrlc ee d co bined with ment properties can be obtained in the practice T102 31.2

of this method, together With'economies in 22.6 pounds of 93% sulfuric acid are then added tion due o re e of handling end e ei and the mixture is rapidly heated to the boiling by controlling the rate of admixture of the titamtemperature and boiled until about 95% of the um sulfate solution and the calcium sulfate slurry 4Q t t is precipitated The composite i i so that the entire admixture is complete in not tate is filt ed or Separated fr the mother 0V6! three minutes, and Preferably wlthlfl one liquor by other means, washed and calcined at a minute, thereafter boiling the mixed solution to temperature of about 0 C precipitate the titanium content of the solution, and calcining the precipitate. Example 2 We believe that the improved results obtained Seventy-five ('75) pounds of commercial lime are due to the fact that the rapid admixture pre- (Cao) are Slaked i 500 pounds of water and vents the formation of S Substantial q the slurry of hydrated lime diluted to 10% conties of colloidal hydrated titanium dioxide in the centratiom o hundred thirty five 35 m as e probably Obtained when the pounds of 66 B. sulfuric acid diluted with 500 tanium solution and the calcium sulfate solution pounds of water are slowly added t t lime are admixed in conventional manner. Since the lurry during period of one h t calcium sulfate particles seem to act as nuclei tinuous agitation, the temperature meanwhile for the hydrolytic precipitation of the hydrated rising to 46 C. The charge is agitated for one T102, the presence of substantial quantities of hour after mixing to ensure complete reaction and then filtered to obtain a more concentrated calcium sulfate pulp, which is then adjusted to a weight of 700 pounds.

To this slurry containing acicular gypsum crystals is added 560 pounds of the titanium solution of Example 1 during a period of 45 seconds. 53 pounds of 90% sulfuric acid is added and the mixture is rapidly heated to the boiling point and boiled for about 5 hours, until 95% of its titanium content is hydrolytically precipitated. The precipitate is filtered, washed and calcined.

While the examples show the precipitation of composite pigments of titanium dioxide and calcium sulfate, in which our new process is most advantageously used, it may also be used to adments in which the extenders act as nucleiifor the precipitation of the hydrated titanium dioxide. By preference, we add the titanium solution to the calcium sulfate slurry, since we have found that best results are obtainedby following this procedure. Y

This application is a continuation in part of our copending application Serial Number 138,104, filed April 21, 1937.

We claim:

l. The steps in the method of preparing composite pigments containing titanium dioxide which comprises mixing a titanium sulfate solution and an aqueous suspension of an extender which acts as a nucleus for the hydrolytic precipitation of hydrated titanium dioxide. under such conditions that the admixture is complete in not over three minutes and immediately thereafter rapidly heating the mixture to a temperature where the titanium content of the solution is hydrolytically precipitated.

2. The steps in the method of preparing composite pigments containing titanium dioxide which comprises mixing a titanium sulfate solution and an aqueous suspension of an extender which acts as a nucleus for the hydrolytic precipitation of hydrated titanium dioxide, under such conditions that the admixture is complete in not over one minute and immediately thereafter rapidly heating the mixture to a temperature where the titanium content of the solution is hydrolytically precipitated.

3. The steps in the method of preparing com posite pigments containing titanium dioxide which comprises mixing a titanium sulfate solution and an aqueous suspension of calcium sulfate, under such conditions that the admixture is complete in not over three minutes and immediately thereafter rapidly heating the mixture to a temperature where the titanium content of the solution is hydrolytically precipitated.

4. The steps in the method of preparing composite pigments containing titanium dioxide which comprises mixing a titanium sulfate solution and an aqueous suspension of calcium sulfate, under such conditions that the admixture is complete in not over one minute and immediately thereafter rapidly heating the mixture to a temperature where the titanium content of the solution is hydrolytically precipitated.

5. The steps in the method of preparing composite pigments containing titanium dioxide which comprises adding a titanium sulfate solution to an aqueous suspension of an extender which acts as a'nucleus for the hydrolytic precipitation of hydrated titanium oxide, during notmore than three minutes and immediately thereafter rapidly heating the mixture to a temperature where the titanium content of the solution is hydrolytically precipitated.

6. The steps in the method of preparing composite pigments containing titanium dioxide which comprises adding a titanium sulfate solution to an aqueous suspension of calcium sulfate, under such conditions that the admixture is complete in not over one minute and immediately thereafter rapidly heating the mixture to a temperature where the titanium content of the solution is hydrolytically precipitated.

'7. The method of preparing composite pigments containing titanium dioxide which comprises mixing a titanium sulfate solution and an aqueous suspension of calcium sulfate, completing the admixture in not over one minute, immediately thereafter rapidly heating the solution to complete the hydrolytic precipitation of the titanium compounds, separating the pigment from the liquid, and calcining the pigment.

LONNIE W. RYAN. WINFRED JOSEPH CAUWENBERG. 

